Chemical modification of lignin and lignin derivatives

ABSTRACT

A method for producing a trans-esterified hydroxypropyl lignin (HPL) is provided in one example embodiment and includes precipitating a lignin, dissolving the precipitated lignin in a solution, adding a reagent to the solution, adjusting the pH of the solution, allowing reactions in the solution to occur for a predetermined amount of time, precipitating the solution to produce a precipitate, and washing, filtering, and drying the precipitate to produce the trans-esterified HPL. In one example, a thermoplastic may be added to produce a trans-esterified HPL/thermoplastic blend.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation and claims the benefit of priorityunder 35 U.S.C. §119(e) to U.S. patent application Ser. No. 13/892,228“CHEMICAL MODIFICATION OF LIGNIN AND LIGNIN DERIVATIVES” filed May 10,2013, and to U.S. Provisional Application Ser. No. 61/646,149, “CHEMICALMODIFICATION OF LIGNIN AND LIGNIN DERIVATIVES FOR BIODEGRADABLE USE”filed May 11, 2012, which are hereby incorporated by reference in theirentirety.

TECHNICAL FIELD

This disclosure relates in general to the field of compositions and,more particularly, to the chemical modification of lignin and ligninderivatives.

BACKGROUND

A plastic material is any of a wide range of synthetic, semi-synthetic,or natural organic solids that may be moldable. Plastics are typicallyorganic polymers of high molecular mass, but they often contain othersubstances. Early plastics were bio-derived materials such as egg andblood proteins, which are organic polymers. In the 1800s, thedevelopment of plastics accelerated with Charles Goodyear's discovery ofvulcanization as a route to thermoset materials derived from naturalrubber. After the First World War, improvements in chemical technologyled to an explosion in new forms of plastics. Among the earliestexamples in the wave of new polymers were polystyrene (PS) and polyvinylchloride (PVC). The development of plastics has come from the use ofnatural plastic materials (e.g., chewing gum, shellac) to the use ofchemically modified natural materials (e.g., rubber, nitrocellulose,collagen, galalite) and finally to completely synthetic molecules (e.g.,bakelite, epoxy, PVC). Plastics are durable and degrade slowly becausethe chemical bonds that make plastic so durable, make it equallyresistant to natural processes of degradation. As a result, most plasticwe use today will either be incinerated or end up in a landfill for manyyears.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified flow diagram illustrating one possible set ofactivities associated with the chemical modification of lignin andlignin derivatives;

FIG. 2 is a simplified flow diagram illustrating one possible set ofactivities associated with the chemical modification of lignin andlignin derivatives;

FIG. 3 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 4 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 5 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 6 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 7 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 8 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 9 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 10 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 11 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 12 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 13 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 14 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 15 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 16 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 17 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 18 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 19 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 20 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives

FIG. 21 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 22 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 23 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 24 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 25 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 26 is a simplified table illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives;

FIG. 27 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives; and

FIG. 28 is a simplified graph illustrating possible example detailsassociated with the chemical modification of lignin and ligninderivatives.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

Lignin is a biopolymer, abundant in nature, and is potentially aninexpensive feedstock material, obtainable as a byproduct of the paperand cellulosic ethanol industries and from a variety of low-valueagricultural commodities such as grasses and straw. In order for ligninto gain wider utilization as an inexpensive andbiodegradable/biorenewable material, blends of lignin withthermoplastics are needed with enhanced mechanical and other usefulproperties. These enhanced properties should exceed those propertiespredictable by simple rules of mixing of the corresponding blends. Asused herein, the term “thermoplastic” includes a polymer that becomespliable or moldable above a specific temperature, and returns to a solidstate upon cooling. Most thermoplastics have a high molecular weight,where chains associate through intermolecular forces.

Generally, transesterification is the process of exchanging the organicgroup R″ of an ester with the organic group R′ of an alcohol. Thereaction can be catalyzed by the addition of an acid or base catalystand can also be accomplished with the help of enzymes (biocatalysts)particularly lipases (E.C.3.1.1.3). For example, in the presence of anacid or base, a lower alcohol may be replaced by a higher alcohol byshifting the equilibrium (e.g., by using large excess of the higheralcohol or by distilling off the lower alcohol). More specifically, asdescribed herein, transesterification can include a method of enhancingthe properties of materials that are comprised of lignin and blendedwith certain thermoplastics by means of a chemical reaction taking placebetween the two polymer components.

In one example, a trans-esterified product may be comprised ofchemically-modified lignin blended with a polyester. For example,transesterification of an acetoxypropyl lignin or a hydroxypropyl ligninmay be used to produce a trans-esterified product. In anotherembodiment, an ester exchange may be used to produce thetrans-esterified product. For example, an acetate ester of the lignin isused to swap carboxylic acid groups with the alcohol oligomer units inthe polyester chains and vice versa. The effect is to covalently-bondpolyester oligomer units (long straight chains) to the lignin while someof the polyester chains would be shortened and terminated with acetateesters. Because the acetoxypropyl lignin has multiple available chemicalfunctional groups, this exchange may happen multiple times.

In an embodiment, chemically-modified lignins may be chosen fromhydroxyalkylated lignins (such as hydroxypropylated lignin) and/oracylated lignins (such as an acetate ester) or other lignin derivedmaterials. In such blends of chemically-modified lignins with certainthermoplastics, transesterification may occur with the replacement ofone alcohol group in the ester linkage by another alcohol group.Accordingly, a hydroxyalkylated lignin may undergo transesterificationwith a nearby polyester macromolecule, thereby transferring a segment ofthe polyester onto the lignin. In addition transesterification (or esterexchange) may occur with an acylated lignin (or acylated andhydroxypropylated lignin). In this instance, an alkyl ester (such as anacetate ester) of the lignin may exchange carboxylic acid groups with analcohol terminated segment of the polyester chain. The effect may be tocovalently-bond long chain polyester segments to the lignin withconcomitant changes in bulk properties.

The resulting properties in the trans-esterified lignin/thermoplasticblends can include increased tensile strength, increased modulus,increased compressive strength, decreased coefficient of thermalexpansion, retarded biodegradability and other properties. It isimportant to note that, in order to retain thermoplastic properties, itis desirable to control or limit the extent of transesterification ofthe lignin/thermoplastic blend such that extensive crosslinking does notoccur. Extensive crosslinking would result in a thermoset which maydecrease or prevent processibility of the lignin/thermoplastic blend(e.g., processibility into films, fibers or molded articles).

In other embodiments, transesterification may be induced to occur duringblending or post-blending by an elevated temperature range, a timeperiod at elevated temperature, and/or the addition of a chemicalcatalyst. The elevated temperature range for transesterification tooccur is chosen from a temperature range above the melting temperatureof the thermoplastic component and from a temperature range below thedecomposition temperature of the lignin component. An estimatedpreferred temperature range can be found between about 150° C. and about250° C., although other ranges could certainly be used in the context ofthe present disclosure. The preferred time at elevated temperature fortransesterification is chosen from a time long enough to causetransesterification to occur while short enough to limit undesirablecrosslinking and/or thermal degradation. An estimated preferred time atelevated temperature for transesterification may be found between about10 minutes and about 48 hours. The chemical catalysts fortransesterification may be chosen from alkali carbonates (such as sodiumcarbonate), zinc acetate, and titanium (IV) butoxide and relatedcompounds. The add-mixture of the transesterification catalyst isestimated to be in the range of 0% to 20% by weight of the material,although other ranges could certainly be used in the context of thepresent disclosure.

In one example embodiment, the chemical modification of lignin andlignin derivatives may be used for a variety of applications. Forexample, the chemical modification of lignin and lignin derivatives maybe used for film products such as bags (e.g., grocery bags, trash bags,etc.), sheets, liners, agricultural films, packaging, etc.; formed andmolded products such as cups and plates, cutlery, bottles etc.;injection molded products such as toys, flower pots, computer cases,automotive parts, etc.; extruded products such as pipes, hoses, tubing,etc., and various other consumer products.

The lignin component biodegrades into humus through an oxidative processby bacteria, fungi, and actinomycetes. Lignin peroxidases, manganeseperoxidases, and laccases are enzymes produced by fungi that contributeto the biodegradation of lignin. An aliphatic polyester component isalso broken down with exposure to natural enzymes such as lipases.Exposure to the natural elements, such as sun and water, may alsoexpedite the degradation process.

In one example implementation, a thin film structural integrity wouldlikely be compromised within 30 to 60 days of exposure to the naturalenvironment. However, different blends can be created that would enablea structure to last longer. More specifically, poly (lactic acid) orpolylactide (PLA) may be added to extend the period of breakdown andthereby extend the life of a product. PLA is a thermoplastic aliphaticpolyester derived from renewable resources, such as cornstarch, tapiocaproducts, or sugarcanes. In addition, a thicker film could also enable astructure to last longer.

The chemical modification of lignin and lignin derivatives may beproduced using acetyoxypropyl lignin (APL) or hydroxypropyl lignin (HPL)trans-esterified with aliphatic polyesters or aliphatic-aromaticcopolymers, or homogenous blends of APL with a biodegradable polymer.The aliphatic polyesters can include polybutylene succinate (PBS),polycaprolactone (PCL), poly lactic acid (PLA), polyhydroxyalkanoate(PHA), aliphatic-aromatic copolymers (AAC), etc. In additionaliphatic-aromatic copolymers (AAC) may also be trans-esterified withAPL or HPL. A sustainable resin may be produced using HPL or APL blendedwith another polymer (nonbiodegradable). The aromatic polyesters can bea modified polyethylene terephthalate (PET), polybutyleneadipate/terephthalate (PBAT), etc.

Hydroxypropyl Lignin (HPL)Where n=1Acetoxypropyl Lignin (APL)Where all OH-groups are replaced by —OAcetyl (CO—CH₃) groups

HPL Overview

In one example implementation, a trans-esterified HPL can include a HPLand a polyester including polyester chains. The polyester may be analiphatic polyester, a semi-aromatic polyester, or an aromaticpolyester. In other examples, an acetate ester of the HPL can be used toswap carboxylic acid groups with the alcohol oligomer units in thepolyester chains. In one implementation, polyester oligomer units arecovalently-bonded to the HPL while one or more of the polyester chainsare shortened and terminated with acetate esters. Further, thetrans-esterified HPL can be represented by the formula R′COOR, whereinR′ represents the HPL and R represents the polyester. In addition,transesterification may occur with the replacement of one alcohol groupin the ester by another different alcohol group.

In another example implementation, a trans-esterified HPL blend caninclude a HPL, a polyester including polyester chains, and one or moreadditives. The one or more additives can be selected from the groupconsisting of catalysts, compatibilizers, odor neutralizers, fragrances,and process aids. The trans-esterified HPL blend may further include aplasticizer. The plasticizer can reduce a glass transition temperatureof the trans-esterified HPL. (The term “glass transition temperature”(or glass-liquid transition temperature) is the temperature at which anamorphous material (or in amorphous regions within semicrystallinematerials) enters a reversible transition from a hard and relativelybrittle state into a molten or rubber-like state.) In oneimplementation, the trans-esterified HPL blend comprises by weight: theHPL in the range of 1% to 99%, the polyester in the range of 1% to 99%,and the one or more additives in the range of 0% to 50% (where the totalpercentage of the HPL, the polyester, and the one or more additivescombined is equal to 100%). Further, the trans-esterified HPL can berepresented by the formula R′COOR, wherein R′ represents the HPL and Rrepresents the polyester. In addition, an acetate ester of the HPL maybe used to swap carboxylic acid groups with the alcohol oligomer unitsin the polyester chains.

In another example implementation, a non-trans-esterified HPL blend caninclude a HPL, a non-trans-esterified polymer, and one or moreadditives. The term “polymer” includes natural or synthetic moleculesmade up of chains or rings of linked monomer units. For example,polyolefins (made from olefin (alkene) monomers), polyesters, amides,urethanes, acrylics, etc. (monomers linked by ester, amide, urethane,acrylate, or other functional groups), natural polymers (e.g.,polysaccharides, protein, DNA, etc.), etc. The one or more additives canbe selected from the group consisting of catalysts, compatibilizers,odor neutralizers, fragrances, and process aids. Thenon-trans-esterified HPL blend may further include a plasticizer. Theplasticizer can reduces a glass transition temperature of thenon-trans-esterified HPL. In one implementation, thenon-trans-esterified HPL blend comprises by weight: the HPL in the rangeof 1% to 99%, the non-trans-esterified polymer in the range of 1% to99%, and the one or more additives in the range of 0% to 50% (where thetotal percentage of the HPL, the non-trans-esterified polymer, and theone or more additives combined is equal to 100%). In anotherimplementation, the non-trans-esterified HPL blend comprises by weight:the HPL in the range of 1% to 99%, the non-trans-esterified polymer inthe range of 1% to 99%, the one or more additives in the range of 0% to50%, and a plasticizer in the range of about 0% to about 50% (where thetotal percentage of the HPL, the non-trans-esterified polymer, the oneor more additives, and the plasticizer combined is equal to 100%). Inaddition, the non-trans-esterified polymer may be selected from thegroup consisting of polyolefins, polyesters, amides, urethanes,acrylics, and polysaccharides.

A method for producing a HPL is provided in one example embodiment andincludes precipitating a lignin, dissolving the precipitated lignin in asolution, adding a reagent to the solution, adjusting the pH of thesolution, allowing reactions in the solution to occur for apredetermined amount of time, precipitating the solution to produce aprecipitate, and washing, filtering, and drying the precipitate toproduce the trans-esterified HPL. The HPL may be a Kraft ligninprecipitated by a Lignoboost process. In one example, the lignin may bedissolved in a sodium hydroxide solution. Further, the sodium hydroxidesolution can be about 4% to about 6% sodium hydroxide. Also, the pH ofthe solution may be adjusted to a range of about 11.5 pH to about 12.5pH. In more particular embodiments, the reagent is propylene oxide. Inaddition, a total weight of the propylene oxide added to the solutionmay be about half a total weight of the precipitated lignin in thesolution. In a specific implementation, the solution may be precipitatedby reducing the pH to below about 2.5 pH. The method may further includeadding sulfuric acid to reduce the pH.

In an example implementation, trans-esterified lignin/thermoplasticblend can include a trans-esterified HPL and a thermoplastic. Thetrans-esterified HPL can be created by precipitating a lignin,dissolving the precipitated lignin in a solution, adding a reagent tothe solution, adjusting the pH of the solution, allowing reactions inthe solution to occur for a predetermined amount of time, precipitatingthe solution to produce a precipitate, and washing, filtering, anddrying the precipitate to produce the trans-esterified HPL. The HPL maybe a Kraft lignin precipitated by a Lignoboost process. In one example,the lignin can be dissolved in a sodium hydroxide solution and thesodium hydroxide solution may be about 4% to about 6% sodium hydroxide.Further, the reagent can be propylene oxide and a total weight of thepropylene oxide added to the solution may be about half a total weightof the precipitated lignin in the solution. In a specific example, thesolution can be precipitated by adding sulfuric acid to reduce the pH tobelow about 2.5 pH.

A method for producing a biodegradable plastic is provided in oneexample embodiment and includes extruding a trans-esterifiedlignin/thermoplastic blend, the trans-esterified lignin/thermoplasticblend including a trans-esterified HPL and a thermoplastic. Thetrans-esterified HPL can be created by precipitating a lignin,dissolving the precipitated lignin in a solution, adding a reagent tothe solution, adjusting the pH of the solution, allowing reactions inthe solution to occur for a predetermined amount of time, precipitatingthe solution to produce a precipitate, and, washing, filtering, anddrying the precipitate to produce the trans-esterified HPL. In oneexample, an alkyl ester of the HPL exchanges carboxylic acid groups withan alcohol terminated segment of a polyester chain such that long chainpolyester segments can be covalently-bond to the HPL. In one particularimplementation, the extent of transesterification of thelignin/thermoplastic blend can be controlled such that extensivecrosslinking does not occur in order to retain thermoplastic properties.Also, the biodegradable plastic may be a film product, a formed andmolded product, an injection molded product, or an extruded product thatbiodegrades over a period of time into humus through an oxidativeprocess. In addition, polylactide may be added to thelignin/thermoplastic blend to extend the period of time that thebiodegradable plastic biodegrades.

APL Overview

In one example implementation, a trans-esterified APL can include an APLand a polyester including polyester chains. The polyester may be analiphatic polyester, a semi-aromatic polyester, or an aromaticpolyester. In other examples, an acetate ester of the APL can be used toswap carboxylic acid groups with the alcohol oligomer units in thepolyester chains. In one implementation, polyester oligomer units arecovalently-bonded to the APL while one or more of the polyester chainsare shortened and terminated with acetate esters. Further, thetrans-esterified APL can be represented by the formula R′COOR, whereinR′ represents the APL and R represents the polyester. In addition,transesterification may occur with the replacement of one alcohol groupin the ester by another different alcohol group.

In another example implementation, a trans-esterified APL blend caninclude a APL, a polyester including polyester chains, and one or moreadditives. The one or more additives can be selected from the groupconsisting of catalysts, compatibilizers, odor neutralizers, fragrances,and process aids. The trans-esterified APL blend may further include aplasticizer. The plasticizer can reduce a glass transition temperatureof the trans-esterified APL. In one implementation, the trans-esterifiedAPL blend comprises by weight: the APL in the range of 1% to 99%, thepolyester in the range of 1% to 99%, and the one or more additives inthe range of 0% to 50% (where the total percentage of the APL, thepolyester, and the one or more additives combined is equal to 100%).Further, the trans-esterified APL can be represented by the formulaR′COOR, wherein R′ represents the APL and R represents the polyester. Inaddition, an alkyl ester of the APL may be used to swap carboxylic acidgroups with the alcohol terminated segment in the polyester chains.

In another example implementation, a non-trans-esterified APL blend caninclude an APL, a non-trans-esterified polymer, and one or moreadditives. The one or more additives can be selected from the groupconsisting of catalysts (e.g., zinc acetate, titanium butoxide, etc.),compatibilizers (e.g., maleaic anhydride, etc.), odor neutralizers(e.g., ADDISPERSE® odor neutralizer concentrate, etc.), fragrances(e.g., FRENCH FRAGRANCES™ apple, FRENCH FRAGRANCES™ french toast, FRENCHFRAGRANCES™ mandarin, etc.), and process aids (e.g., slip, erucamide,oleamide, antiblock, calcium carbonate, silica, talc etc.). Thenon-trans-esterified APL blend may further include a plasticizer (e.g.,biodegradable such as alkyl citrates, acetyl tributyl cirtrate (ATBC),acetyl triethyl cirtrate, acetylated monoglycerides, etc. ornon-biodegradable such as phthalates, diisooctyl phthalate (DIOP),glycols, etc.). The plasticizer can reduce a glass transitiontemperature of the non-trans-esterified APL. In one implementation, thenon-trans-esterified APL blend comprises by weight: the APL in the rangeof 1% to 99%, the non-trans-esterified polymer in the range of 1% to99%, and the one or more additives in the range of 0% to 50% (where thetotal percentage of the APL, the non-trans-esterified polymer, and theone or more additives combined is equal to 100%). In anotherimplementation, the non-trans-esterified APL blend comprises by weight:the APL in the range of 1% to 99%, the non-trans-esterified polymer inthe range of 1% to 99%, the one or more additives in the range of 0% to50%, and a plasticizer in the range of about 0% to about 50% (where thetotal percentage of the APL, the non-trans-esterified polymer, the oneor more additives, and the plasticizer combined is equal to 100%). Inaddition, the non-trans-esterified polymer may be selected from thegroup consisting of polyolefins, polyesters, amides, urethanes, acrylicsand polysaccharides.

A method for producing an APL is provided in one example embodiment andincludes mixing a solvent, a catalyst, a reagent, and a HPL to create asolution, raising the temperature of the solution to a first reactiontemperature, raising the temperature of the solution to a secondreaction temperature, allowing reactions in the solution to occur for apredetermined amount of time, precipitating the solution to produce aprecipitate, and washing, filtering, and drying the precipitate toproduce the APL. The HPL can contain about three percent moisture. In anexample, the solvent is a fifty percent acetic acid solution. Also, thecatalyst may be sodium acetate. Further, the reagent may be a fiftypercent acetic anhydride solution. In one implementation, the method mayfurther include dissolving the catalyst in the solvent to create asolvent catalyst solution, where the catalyst may be sodium acetate andthe solvent can be a fifty percent acetic acid solution, adding the HPLto the solvent catalyst solution, and adding the reagent to the solventcatalyst solution that contains the HPL, where the reagent may be afifty percent acetic anhydride solution. In addition, the amount of HPLadded to the solvent catalyst solution can be about thirty percent of atotal weight of the solvent catalyst solution. In a specific example,the solution can be precipitated by adding a volume of the solution intoa volume of ice water. The volume of the ice water may be five times thevolume of the solution. The precipitate can be dried in auntil theprecipitate contains about three percent moisture. In one example, theprecipitate is dried in a convection oven.

In another example implementation, a trans-esterifiedlignin/thermoplastic blend can include a trans-esterified lignin and athermoplastic. The trans-esterified lignin can be an APL created byadding a solvent, a catalyst, and a reagent to a HPL, raising thetemperature of the solution to a first reaction temperature, raising thetemperature of the solution to a second reaction temperature, allowingthe reactions in the solution to occur for a predetermined amount oftime, precipitating the solution to produce a precipitate, and washing,filtering, and drying the precipitate to produce the APL. In an example,the solvent may be a 50% acetic acid solution, the catalyst may besodium acetate, and the reagent may be a 50% acetic anhydride solution.In one implementation, the catalyst can be dissolved in the solvent tocreate a solvent catalyst solution, where the catalyst may be sodiumacetate and the solvent can be a 50% acetic acid solution. The HPL maybe added to the solvent catalyst solution and the reagent can be addedto the solvent catalyst solution that contains the HPL. The reagent maybe a 50% acetic anhydride solution. In addition, the solution may beprecipitated by adding a volume of the solution into a volume of icewater. The volume of the ice water may be five times the volume of thesolution. The precipitate can be dried until the precipitate containsabout 3% moisture. In one example, the precipitate is dried in aconvection oven.

A method for producing a biodegradable plastic is provided in oneexample embodiment and includes extruding a trans-esterifiedlignin/thermoplastic blend, the trans-esterified lignin/thermoplasticblend including a trans-esterified APL and a thermoplastic. Thetrans-esterified APL can be created by adding a solvent, a catalyst, anda reagent to a HPL, raising the temperature of the solution to a firstreaction temperature, raising the temperature of the solution to asecond reaction temperature, allowing the reactions in the solution tooccur for a predetermined amount of time, precipitating the solution toproduce a precipitate, and washing, filtering, and drying theprecipitate to produce the APL. In one example, an alkyl ester of theHPL exchanges carboxylic acid groups with an alcohol terminated segmentof a polyester chain such that long chain polyester segments can becovalently-bond to the HPL. In one particular implementation, the extentof transesterification of the lignin/thermoplastic blend can becontrolled such that extensive crosslinking does not occur in order toretain thermoplastic properties. Also, the biodegradable plastic may bea film product, a formed and molded product, an injection moldedproduct, or an extruded product that biodegrades over a period of timeinto humus through an oxidative process. In addition, polylactide may beadded to the lignin/thermoplastic blend to extend the period of timethat the biodegradable plastic biodegrades.

Example Embodiments

Turning to FIG. 1, FIG. 1 is a simplified flowchart 100 illustratingexample activities associated with the chemical modification of ligninand lignin derivatives. At 102, a lignin is precipitated. For example, aKraft lignin may be precipitated using a Lignoboost process or someother lignin precipitation process. At 104, the lignin is dissolved in asolution. For example, the lignin may be dissolved in a sodium hydroxide(NaOH) solution. The solution should contain sufficient NaOH to convertthe lignin into lignate by neutralizing the available acidic groups(such as phenolic and carboxylic functionalities) and raising the pH ofthe solution to greater than 8 pH. In one example, the NaOH solution maybe about 4% to about 6% NaOH. At 106, the pH of the solution is adjustedto a desired range. For example, the desired range may be between about10.0 pH to about a 12.5 pH. At 108, a reagent is added. In one example,the reagent is propylene oxide (CH₃CHCH₂O). More specifically a one totwo ratio (1:2) of propylene oxide per lignin may be used (e.g., aboutfifty pounds (50 lbs) of propylene oxide to about one hundred pounds(100 lbs) of lignin).

At 110, the solution is monitored to keep the temperature of thesolution within a desired temperature range and the pH of the solutionwithin a desired pH range. For example, the solution may be monitoredfor about four (4) to about six (6) hours to keep the temperature rangebetween about 15° C. and about 25° C. (to make sure the propylene oxidedoes not flash off) and the pH between about 10.0 pH and about 12.5 pHto facilitate the reaction. Diluted sulfuric acid (H₂SO₄) may be used tocontrol the pH. At 112, reactions in the solution are allowed to takeplace for a predetermined amount of time. For example, the solution maysit for twelve (12) hours to allow the reactions to complete or almostcomplete. At 114, the solution is precipitated by reducing the pH of thesolution. For example, concentrated H₂SO₄ may be added to reduce the pHbelow about pH 2.5 to trigger the precipitation of the modified lignin.At 116, the resulting precipitate is filtered, washed, and dried. Forexample, the precipitate may be pumped into a filter press and washedwith deionized water (H₂O). The precipitate may then be placed in adryer where the drying temperature can be between about 40° C. to about100° C. or higher. The dryer may contain one or more agitators to helpfacilitate drying. In addition, vacuum may be applied to help facilitatethe drying. The chemically modified lignin may be removed when themoisture of the chemically modified lignin is below about 3%. In oneexample, the above described process may be done under atmosphericconditions with an inert gas (e.g., argon or nitrogen) pad.

It should be noted that the modification of the lignin (as describedherein) can take place entirely in an aqueous solution. In addition, thetemperature and pH are controlled during the process. This allows forlarger batches of HPL to be produced, the usage of propylene oxide to beenhanced, reduction in propylene glycol produced, and improvedfiltering. The processes described herein allows for a consistentlyproduceable, filterable HPL product, on a relatively large scale.

Turning to FIG. 2, FIG. 2 is a simplified flowchart 200 illustratingexample activities associated with the chemical modification of ligninand lignin derivatives. At 202, a solvent, catalysts, and reagent areadded to a hydroxypropylated lignin (HPL) to create a solution. Forexample, about 50% acetic acid may be used as the solvent, sodiumacetate may be used as the catalyst, and 50% acetic anhydride may beused as the reagent. In one example, the HPL is dried to about 3%moisture. While the order of adding the solvent, catalyst, reagent, andHPL does not affect the process, in one implementation, the catalyst isfirst dissolved in the solvent. Then the lignin is added where theamount of lignin added is about 30% of the total weight of the solution(i.e., the catalyst and the solvent). Next, the reagent is added to thesolution.

At 204, the temperature of the solution is raised to a first reactiontemperature and the pH of the solution is kept within a desired range.For example, the temperature of the solution may be raised to a firstreaction temperature of about 50° C. and the desired range of pH can bein the acidic range (e.g., a pH of 2 or 3). At 206, the temperature ofthe solution is raised to a second reaction temperature. For example,the second reaction temperature may be about 70° C. At 208, reactions inthe solution are allowed to take place for a predetermined amount oftime. For example, the solution may sit for twelve (12) hours to allowthe reactions to complete or almost complete.

At 210, the solution is precipitated. For example, the solution may beprecipitated by introducing a small stream of the solution into arelatively large volume of ice water. In one implementation, the largevolume of ice water is about five (5) times the volume of solution. Inan example, the solution is vigorously stirred as the solution entersthe ice water to facilitate contact with the ice water and produce adesired precipitation and particle size. At 212, the resultingprecipitate is filtered, washed, and dried. For example, the solutionmay be filtered in a Büchner funnel or some other similar type filter.The precipitate may be washed (in one example at least two times) withdeionized water to wash out impurities such as acetic acid. The washedprecipitate may be dried in a convection oven until the moisture of theprecipitate is about 3% moisture or less.

The disclosed modified lignin and lignin derivatives may be blended witha thermoplastic to produce a trans-esterified lignin/thermoplasticblend. The extrusion is done at a temperature that will not degrade themodified lignin (e.g., in a temperature range of about 110° C. to about180° C.). In an example, the extrusion rate (dwell time in the extruder)is at least ten (10) minutes but less than sixty (60) minutes to ensureno degradation of the modified lignin occurs during extrusionprocessing. The trans-esterified lignin/thermoplastic blend may be usedfor film products such as bags (e.g., grocery bags, trash bags, etc.),sheets, liners, agricultural films, packaging, etc.; formed and moldedproducts such as cups and plates, cutlery, bottles etc.; injectionmolded products such as toys, flower pots, computer cases, automotiveparts, etc.; extruded products such as pipes, hoses, tubing, etc., andvarious other consumer products.

In an illustrative example, various trans-esterifiedlignin/thermoplastic blends were extruded on a THEYSOHN® TSK 21 mm twinscrew extruder. Pellets of the trans-esterified lignin/thermoplasticblends were separately placed in a desiccant dryer overnight prior toblow extrusion. The pellets were blown on a 1.5″ single screw extruderwith a 2″ vertical blown film air die. About 10 pounds each of 30% HPL,70% aliphatic polyester and 30% HPL, 70% metallocene catalyzed lowdensity polyethylene were cast extruded on a 1.5″ single screw extruderwith an 8″ die with rollers. The modified lignin can be blended withthermoplastics such as polypropylene (PP), low density polyethylene(LDPE), linear low-density polyethylene (LLDPE), high densitypolyethylene (HDPE), ethylene vinyl acetate (EVA), ECOVIO®, ECOFLEX®,polyethylene glycol (PEG), poly butylene succinate (PBS), polyethyleneterephthalate (PET), polyhydroxyalkanoates (PHAs), polybutyl acrylate(PBA), polylactic acid or polylactide (PLA), etc.

The HPL was placed in fifty-five (55) gallons drums and filtered andwashed on a 470 mm filter press. The HPL cakes had a moisture content ofabout 48%. The cakes were left in open air for about forty-eight (48)hours that reduced the moisture to about 25%. The cakes were then driedon a 40 L Helical dryer to a moisture content of 2.5%. The dry HPL waspackaged and shipped for processing.

The pellets were compounded on a THEYSOHN® TSK 21 mm twin screw extruderat PCE. The carrier resin was fed through a hopper, and the HPL powderwas side fed about mid-way through the screw. The compounded strand wascooled with two (2) water baths and had an air knife to blow off excesswater before being cut into pellets.

Prior to blow extrusion, the pellets were placed in a desiccant dryerovernight to reduce the moisture to below 0.05%. The pellets were blownon a 1.5″ single screw extruder with a 2″ vertical blown film air die.About 10 pounds of the 30:70 HPL:Eco and HPL:LDM were cast extruded onthe 1.5″ single screw extruder with an 8″ die with rollers. A goodtemperature range for compounding and converting the HPL is around about270° F. to about 350° F. The carrier resins that blended best with theHPL had melt temperatures in or below that zone.

Lignin Chemical Modification Reactions

HPL 1^(st) Preparation

A 3.0 L 3-necked, round-bottomed flask was assembled with an overheadstirrer and equipped with a Friedrich condenser and a water-jacketedaddition funnel. Chilled water was circulated through the condenser andthe jacket of the addition funnel. The reactor was charged with a 6 wt %aqueous sodium hydroxide solution (500 mL). The lignin was added inportions until it was completely dissolved in a viscous dark brownmixture. The pH was about 11.0 as indicated by pHYDRION® pH 1-14indicator paper, slightly dampened with distilled water. To the additionfunnel was added 125 g of propylene oxide which was then added dropwiseover a period of one hour to the stirred mixture. The reaction wasstirred at room temperature for 48 hours. When the reaction wascomplete, argon was bubbled through the mixture for about 30 min todrive off the excess propylene oxide. With the flask chilled in an icebath, dilute (about 7%) sulfuric acid was added until the pH of themixture was about 2.0 (as indicated by pHYDRION® paper, 1-14 pH range).The mixture was allowed to settle overnight and the supernatant wasdecanted from the precipitate. About 1.0 L of deionized water was addedwith stirring. The yellow cloudy supernatant suspension was removed bycentrifugation. The washing was repeated 2 more times. Then, the browninsoluble material was re-suspended in water and freeze dried to afford65 g (26% of the original weight) of light brown powder.

HPL 2^(nd) Preparation

A 3-necked 12 L round-bottomed flask with a bottom stopcock, wasassembled with 5 ft. of ⅜ id polyethylene internal cooling coils, aFriedrich condenser, a 100 mL jacketed addition funnel and an overheadstirrer connected by a flexible mechanical cable to a variable speedstir motor.

The internal coils were connected to a re-circulating heater/chiller.The Friedrich condenser and jacketed addition funnel were connected toeach other in series and to a second re-circulating heater/chiller. Intothe 12 L flask was placed a solution of 60 g of sodium hydroxide in 4.0L of deionized water. The pH of the solution was then adjusted to a pHof 11.5 (as indicated by pHYDRION® paper, 9 to 13 pH range) by thecareful addition of 10% hydrochloric acid, thus increasing the solutionvolume to about 4.4 L. The solution was cooled by circulating chilled(20° C.) coolant (ethylene glycol/water) through the internal coils. Alignin powder isolated from a spent alkaline pulping liquor (1.3 kg) wasthen added in small portions through a large long stem funnel while thesolution was vigorously stirred. When all of the lignin had been added,the pH was then readjusted to a pH of 11.0. The Friedrich condenser andthe addition funnel were cooled by circulating chilled (0° C.) coolant(ethylene glycol/water). A one-holed stopper was placed in the top ofthe addition funnel and the stem of a separatory funnel, supported by aring, was placed through the hole. (Thus the liquid from the separatoryfunnel could replenish the liquid in the addition funnel as it wasdispensed dropwise into the reaction mixture.)

To the separatory funnel and jacketed addition funnel were added 500 mLof propylene oxide (SIGMA-ALDRICH® Chemical Co, previously chilledovernight in a refrigerator). The cold propylene oxide was addeddropwise over a period of about 2 hours to the stirred reaction mixture.Stirring of the mixture was continued overnight at 20° C. under a 0° C.cooled reflux condenser. The next day, the pH of the mixture was againadjusted to pH 11.0 (as indicated by pHYDRION® paper in the 9 to 13 pHrange) by the addition of 10% hydrochloric acid and stirring wascontinued for an additional 24 hours (48 hours total), at 25° C. At theconclusion of the reaction, the reflux (Friedrich) condenser was removedand the temperature of the internal coils was increased to 45° C. as avigorous stream of argon (>5 L min) was passed over the reaction mixturefor 30 min to drive off any un-reacted propylene oxide.

The reaction mixture was then drained through the bottom stopcock portinto a 20 L polyethylene bucket (precipitation tank). An overheadstirrer with a large paddle was used to vigorously stir the mixture inthe bucket as dilute, room-temperature sulfuric acid (about 150 mL in150 mL of distilled water) was added in portions until a pH of 2.0 (asindicated by pHYDRION® 1-14 paper) was achieved. When the acidificationwas complete, the initially dark brown solution had become a lighterbrown suspension as lignin precipitated.

The modified lignin was separated from the supernatant in about 1.0 Lportions by filling four 250 mL polyethylene bottles with the brownsuspension, balancing the opposing bottles, and centrifuging at 4000 rpmfor 30 min. Brown solid pellets were collected in eight bottles. Thecontents of each bottle were washed with 3×200 mL of water byre-suspending the pellets in distilled water and re-centrifuging. Thecollected solid was divided into two halves (4 bottles per half). Eachhalf was re-suspended in about 1 L of water, filtered through astainless steel mesh to remove lumps and freeze dried (−86° C.condenser, 0.007 torr, 48 h, until 299 g (23% of the starting weight) ofa fine light brown powder was obtained.

HPL 3^(rd) Preparation

A concentration of sodium hydroxide was reduced to 5% and diluted 4Nsulfuric acid was used for pH control. (In the precipitation stageconcentrated sulfuric acid was used.) A 100 gal Ross mixer was equippedwith an anchor agitator and a dispersing agitator.

Sodium hydroxide pellets were added to ice cold water in the Ross mixerprior to the addition of lignin. Once all the sodium hydroxide pelletswere dissolved, the lignin was added in 20 to 23 lb-portions at a timeover a period of about one and a half hours. FIG. 3 illustrates possibleexample details associated with the addition over lignin over time.

Once all the lignin had dissolved, the pH of the solution was adjusteddown to a pH of 11.5 with the addition of 4N sulfuric acid. FIG. 4illustrates possible example details associated with the pH adjustmentover time.

After the pH was adjusted, propylene oxide (PO) was added. The PO wasadded over a period of an hour and a half. As illustrated in FIG. 5, thepH was monitored throughout the addition and adjusted as necessary with4N sulfuric acid.

The reaction was allowed to run overnight. As illustrated in FIG. 6,during the first 4 hours of the reaction, the pH was monitored andadjusted as necessary with 4N sulfuric acid. FIG. 7 illustrates possibleexample details associated with the pH adjustment over time.

After allowing the reaction to sit overnight, the product wasprecipitated by adding concentrated sulfuric acid to lower the pH tobelow 2.5. The sulfuric acid was added over a period of two and a halfhours, as illustrated in FIG. 8. FIG. 9 illustrates possible exampledetails associated with the pH adjustment over time.

The mixture was placed in drums and sent to ANDRITZ® in Florence, Ky.for filtering and drying. Filtering was performed via a filter press.Cakes were formed in the filter press and washed by pumping waterthrough the cakes while still in the filter press. A helical dryer wasused. However, it was not able to dry the cakes straight from the filterpress. The cakes had to be crumbled and spread out to air dry. Once thecakes air dried to about 25% moisture, the helical dryer was able to drythe product to less than 3% moisture.

The lignin had contaminants ranging from straw to rocks which did nothelp the reaction and also caused a failure of the transfer pump used topump the product from the Ross mixer to 55 gallon drums. Carefulmonitoring and control of temperature can result in a consistentproduct. Nuclear magnetic resonance (NMR) showed that there was acomplete reaction of the Kraft lignin to HPL.

HPL 4^(th) Preparation

A concentration of sodium hydroxide was reduced to 5% and diluted 4Nsulfuric acid was used for pH control. (For the precipitation stage,concentrated sulfuric acid was used.) Ice (or ice bath) was used tocontrol temperature during the reaction. The lignin was sifted prior tobeing added to the sodium hydroxide solution. A 100 gal Ross mixer wasequipped with an anchor agitator and a dispersing agitator.

Sodium hydroxide pellets were added to ice cold water in the Ross mixerprior to the addition of lignin. Once all the sodium hydroxide pelletswere dissolved, the lignin was added over a period of about one hour andfifteen minutes. FIG. 10 illustrates possible example details associatedwith the addition of lignin over time.

Once all the lignin had dissolved, the pH of the solution was adjusteddown to a pH of 11.5 with the addition of 4N sulfuric acid. FIG. 11illustrates possible example details associated with the pH adjustmentover time.

After the pH was adjusted, propylene oxide (PO) was added through a portat the top of the Ross mixer. As illustrated in FIG. 12, the PO wasadded over a period of an hour and twenty minutes. The pH was monitoredthroughout the addition and adjusted as necessary with 4N sulfuric acid.

The reaction was allowed to run overnight. During the first 4 hours ofthe reaction the pH was monitored and adjusted as necessary with 4Nsulfuric acid. The temperature was also monitored and adjusted by theaddition of ice. FIGS. 13 and 14 illustrates possible example detailsassociated with monitoring and adjusting the pH as necessary with 4Nsulfuric acid and with monitoring and adjusting the temperature asnecessary with ice.

After allowing the reaction to run overnight, the product wasprecipitated by adding concentrated sulfuric acid to lower the pH tobelow 2.0, as illustrated in FIG. 16. As illustrated in FIG. 15, thesulfuric acid was added over a period of about 3 hours.

The mixture was placed in drums and sent to ANDRITZ® in Florence, Ky.for filtering and drying. Filtering was performed via a filter press.Cakes were formed in the filtered press and washed by pumping waterthrough the cakes while still in the filter press. The dryer used forthis batch was a helical dryer. The helical dryer was not able to drythe cakes straight from the filter press and the cakes had to becrumbled and spread out to air dry. Once the cakes air dried to about25% moisture the helical was able to dry the product to less than 3%moisture.

Sifting the lignin allowed it dissolve much easier in the alkalisolution. Controlling the temperature and pH through the reactionproduced a better precipitate and the precipitated particles werelarger. NMR showed that there was a complete reaction of the Kraftlignin to HPL.

APL 1^(st) Preparation

A 1.0 L, 3-necked flask was equipped with a magnetic stirrer, with alarge football-shaped stir bar, and with a tap-water-cooled refluxcondenser. In the flask were placed acetic anhydride (100 mL, ^(˜)1.0mol), acetic acid (100 mL) and sodium acetate (8.04 g, ^(˜)0.1 mmol).HPL (about 40.0 g) was then added in small portions to the stirredsolution until all the lignin had dissolved. The openings in theapparatus were stoppered with rubber septa and then needles,needle-to-tubing adapters, and an oil bubbler were used to establish anargon atmosphere (anhydrous, industrial grade) within the apparatus. Themixture was stirred for 48 hours at room temperature and then refluxedfor 1 hour. Upon cooling to room temperature, the mixture was pouredinto 2.0 L of ice water and the resulting precipitate was collected on amedium porosity sintered glass Buchner funnel, with suction. Thecollected solid was placed in a glass vessel. The glass vessel with thecollected solid was placed in a vacuum oven containing a tray of about100 g of sodium hydroxide desiccant and then dried in vacuo for 72 hoursat 40° C. to produce 39.3 g (98.3% of the starting weight) of dark brownsolid particles.

APL 2^(nd) Preparation

HPL was dried in a vacuum oven prior to being used and the moisture wastested to be below 3%. Acetic acid was used as the solvent. Aceticanhydride was used as the reagent. Sodium acetate was added as acatalyst.

The apparatus used was a 12 L 3-neck round bottom flask with a bottomstopcock. An overhead stirrer was used to agitate the mixture. An argonpad was used to reduce the amount of acetic anhydride reacting withmoisture from the atmosphere.

3.5 L of acetic acid was measured out and added to the 12 L flask. Nextthe sodium acetate was added to the flask with agitation. Then, 100 g ofsodium acetate and the catalyst were added to the acetic acid withagitation. The sodium acetate dissolved after approximately 20 minutes.1.75 kg of HPL was then added to the flask. After about 30 minutes theHPL had dissolved. Then, 3.5 L of acetic anhydride, the reagent, wasadded. After all components were added to the solution, the solution washeated to 50° C. This took approximately one hour. The solution was thenheated to 70° C. The solution was stirred overnight with heating toensure complete reaction.

After allowing the reaction to sit overnight, the solution was thencooled to below 50° C. to prepare for precipitation. The APL was thenprecipitated by opening the stopcock to add a small steady stream ofsolution to flow into a highly agitated 5-gallon bucket of ice water.The ice water consisted of about 5 kg of ice and 8 kg of water. Half ofthe solution was precipitated in one bucket of ice water. A secondbucket of ice water was used to precipitate the rest of the solution.

The buckets of precipitated APL were poured into a 2-foot diameterBuchner funnel for filtering. The APL formed a porous cake as thefiltrate drained through the filter. Water was then added to wash theAPL cake while it was in the Buchner funnel. Then, about 2.5 gallons ofwater was added to the Buchner funnel and allowed to drain. This washingstep was repeated 2 to 5 times until the filtrate became clear and theacetic acid odor became less noticeable. The cake was then collected inaluminum pans and placed into a convection oven to dry at 50° C.

Drying the HPL prior to the reaction allowed the use of less aceticanhydride as excess moisture reacts with acetic anhydride turning itinto acetic acid. Heating speeds up the reaction. Also, the addition ofcatalyst speeds up the reaction. APL is less hygroscopic than HPL anddries nicely in a convection oven unlike HPL. The resulting product isfriable and crumbles into a fine powder. NMR showed that there was acomplete reaction of HPL to APL.

APL and Aliphatic Polyester Blend

Mixtures of APL powder (55% by weight) with EcoflexTm aliphaticpolyester pellets (45% by weight) were dry-blended in amounts to load(about 65 g, according to a mixer manufacturer's formula) a HaakeRheoflex 90 rheometer/mixer. The mixtures and catalyst/additives (ifany) are added in portions at slow mixing speeds and then blended in theHaake mixer at 130° C. for about fifteen (15) minutes at about 75 rpmmixing speed and then each batch was removed from the mixer and allowedto cool. Transesterification experiments were conducted by reintroducingapprox. 60 g of each batch to the Haake mixer while varying thefollowing conditions:

a. chemical catalyst:

-   -   i. no catalyst    -   ii. zinc acetate (1 wt %) and titanium(IV)butoxide (1 wt %)

b. transesterification temperatures

-   -   i. 200° C.    -   ii. 225° C.    -   iii. 250° C.

c. transesterification times

-   -   i. 10 min.    -   ii. 30 min.    -   iii. 60 min.

Each batch was removed from the mixer, cooled and analyzed.

Melt compounded samples prepared in Example 1 were hot-pressed into 6in×6 in×0.05 in steel molds using a TETRAHEDRON® Associates, Inc.programmable hot-press and using FREECOAT™ 770-NC mold release. Thesheets were pressed at 260° F. at 9000 psi for 15 minutes. Manuelbumping cycles were applied to produce uniform void-free sheets.

“Dog bone” specimens were punched from the sheets using a ASTM D412 diepunch and tested according to ASTM D412 testing standards (the term “dogbone” is used as it is known in the art of tensile testing). The resultsare shown in FIGS. 17-28 below:

The above data indicates that for 55%/45% APL/Ecoflex blends additionheating and blending at around 200° C. for under 30 min can improvetensile strength of the blended material. The data also indicates thatfor materials blended at 130° C. for 15 minutes, the addition of 1% zincacetate and 1% titanium (IV) butoxide catalysts can improve the tensilestrength of the blends.

It is imperative to note that the operations and steps described withreference to the preceding FIGURES illustrate only some of the possiblescenarios that may be executed by, or within, the systems of the presentdisclosure. Some of these operations may be deleted or removed whereappropriate, or these steps may be modified or changed considerablywithout departing from the scope of the discussed concepts. In addition,the timing of these operations may be altered considerably and stillachieve the results taught in this disclosure. The preceding discussionshave been offered for purposes of example and discussion. Substantialflexibility is provided by the system in that any suitable arrangements,chronologies, configurations, and timing mechanisms may be providedwithout departing from the teachings of the discussed concepts. Alongsimilar lines, the ranges (e.g., with respect to timing, temperature,concentrations, etc.) could be varied considerably without departingfrom the scope of the present disclosure.

Numerous other changes, substitutions, variations, alterations, andmodifications may be ascertained to one skilled in the art and it isintended that the present disclosure encompasses all such changes,substitutions, variations, alterations, and modifications as fallingwithin the scope of the appended claims. In order to assist the UnitedStates Patent and Trademark Office (USPTO) and, additionally, anyreaders of any patent issued on this application in interpreting theclaims appended hereto, Applicant wishes to note that the Applicant: (a)does not intend any of the appended claims to invoke paragraph six (6)of 35 U.S.C. section 112 as it exists on the date of the filing hereofunless the words “means for” or “step for” are specifically used in theparticular claims; and (b) does not intend, by any statement in thespecification, to limit this disclosure in any way that is not otherwisereflected in the appended claims.

What is claimed is:
 1. A method for producing a biodegradable plastic,the method comprising: extruding a trans-esterified lignin/thermoplasticblend, the trans-esterified lignin/thermoplastic blend comprising: atrans-esterified hydroxypropyl lignin (HPL), wherein thetrans-esterified HPL is created by: precipitating a lignin; dissolvingthe precipitated lignin in a solution; adding a reagent to the solution;adjusting a pH of the solution; allowing reactions in the solution tooccur for a predetermined amount of time such that the lignin hasundergone transesterification with a nearby polyester macromolecule froma polyester, thereby transferring a segment of the polyester onto thelignin; precipitating the solution to produce a precipitate; andwashing, filtering, and drying the precipitate to produce thelignin/thermoplastic polyester blend.
 2. The method of claim 1, whereinan alkyl ester of the HPL exchanges carboxylic acid groups with analcohol terminated segment of a polyester chain such that long chainpolyester segments are covalently-bond to the HPL.
 3. The method ofclaim 1, wherein the extent of transesterification of thelignin/thermoplastic blend is controlled such that extensivecrosslinking does not occur in order to retain thermoplastic properties.4. The method of claim 1, wherein the biodegradable plastic is a filmproduct, a formed and molded product, an injection molded product, or anextruded product that biodegrades over a period of time into humusthrough an oxidative process.
 5. The method of claim 4, whereinpolylactide is added to the lignin/thermoplastic blend to extend theperiod of time that the biodegradable plastic biodegrades.